Honing machine



Nov. 22, 1966 D. K. GREENBERG 3,286,409

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L e ML5 LT-x m l- L4 ZDonad G "g 7 5 United States Patent 3,286,409 HONING MACHINE Donald K. Greenberg, Rockford, Ill., assignor to Barnes Drill Co., Rockford, 11]., a corporation of Illinois Filed Mar. 27, 1964, Ser. No. 355,269 Claims. (Cl. 51--165) This invention relates to honing machines for enlarging bores in workpieces in a honing cycle including the steps of reciprocating a honing tool back and forth through the bore while rotating and expanding the tool, gaging the progressive enlargement of the bore with a device which senses the attainment of a predetermined bore size, and initiating the termination of the honing cycle in response to attainment of the predetermined bore size. The invention has more particular reference to honing machines in which the operation of the honing tool is varied in the course of the honing cycle to vary the character of the honing action during the final portion of the cycle.

In prior machines of this general type, it has been impossible to obtain a precise finished bore size because the amount of work stock removed during the final portion of the honing cycle, and the determination of the finished bore size and the quality of the finish therefore have been largely a matter of guesswork and approximation. Accordingly, a general object of the present invention is to eliminate such guesswork and approximation in the finishing of work bores that are rough and finish honed in a substantially continuous operation.

The primary object of the invention is to remove stock from bore walls by successive rough and finish honing operations in a substantially continuous cycle and terminate the honing in response to the attainment of a precise finished bore size.

A more detailed object is to provide a honing machine of the above character in which the rough and finish honing operations are controlled by a successively acting sizing device for sensing and signaling not only the attainment of the desired rough honed size but also the precise finish honed size.

Another object is to disable the rough sizing means in response to attainment of the desired rough size and activate the finish sizing means to sense and signal the attainment of the finished bore size.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a fragmentary side elevational view of the head and tool of a honing machine embodying the novel features of the present invention with parts broken away and shown in cross-section.

FIG. 2 is a fragmentary cross-sectional view taken along the line 2-2 of FIG. 3.

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view similar to FIG. 2 with parts in moved positions.

FIG. 5 is an exploded perspective view of the sizing plugs.

FIG. 6 is a schematic view of the drive mechanism for the hone.

FIG. 7 is a schematic view of an alternate form of the sizing device.

FIGS. 8a and 8b are schematic views which, when placed end to end, show an electric control circuit for the machine.

As shown in the drawings for purposes of illustration, the invention is embodied in a production type honing machine in which a honing tool 10 is carried on the lower end of a jointed shank 11 coupled to a spindle 12 "ice journaled on a hollow head 13 which is slidable vertically relative to the machine frame 16 toward and away from the end of a bore 14 in a workpiece 15 supported in a suitable fixture (not shown) below the head. The spindle is rotated by an electric motor 17 (FIG. 8a) mounted on the frame with its splined shaft 18 geared to the spindle at 19 and the head is raised and lowered by a reciprocating hydraulic actuator 20 comprising a piston 21 slidably guided in a vertical cylinder 22 mounted on the frame with the piston rod 23 connected to a lug 24 fast on the head. Pressure fluid is supplied alternately to the opposite ends of the cylinder by a pump (not shown) driven by a motor 25 thereby to lower the head, insert the hone 10 in the work bore 14 and then reciprocate the hone back and forth through the bore.

The honing tool 10 comprises a series of abrasive stones 27 (FIG. 1) angularly spaced around a generally cylindrical body 28 fast on the lower end of the shank 11. Each stone is held frictionally in a slot in the body and is mounted on a follower 29 which abuts on its inner side against a conical cam 30 formed on the lower end of a rod 31 extending upwardly through the tool shank, the spindle 12 and the head 13. When the hone is disposed within the work bore 14, the rod is shifted downwardly relative to the hone to cam the followers and the stones radially outwardly and expand the hone at a rate determined by the rate of axial movement of the rod.

While the feed mechanism for producing the axial motion of the rod 31 relative to the hone 10 may take various forms, the mechanism shown herein for purposes of illustration is of the type including a nut 32 (see FIGS. 1 and 6) threaded onto the upper end of the rod and journaled in a fixed axial position in a housing 33 (FIGS. 1 and 8a) constituting an extension of the head 13. The outer toothed periphery of the nut forms a worm wheel 34 which meshes with a worm 35 fast on a shaft 37 journaled in the housing for rotation about an axis perpendicular to the rod axis adjacent the upper end of the rod. This shaft is adapted to be rotated at different selected speeds by two electric motors 38 and 39 (FIGS. 1, 6 and 8b) through suitable reduction gearing in the housing. The motor 38 expands and collapses the hone rapidly at the beginning and end of each honing cycle while the motor 39 produces the gradual feeding of the stones 27 into the work during the honing cycle.

Herein, the rapid expand motor 38 is disposed within the housing 33 with its shaft 40 carrying a gear 41 (FIG. 6) meshing with an idler gear 42 which meshes with and drives a third gear 43 fast on the drive shaft 37 of the expansion mechanism. The feed motor 39 is mounted on the outside of the housing 33 as shown in FIG. 1, and its shaft turns a worm 44 meshing with a worm wheel 45 on one end of a perpendicular shaft 47 projecting into the housing and journaled in suitable bearings therein. On the other end of this shaft is a worm 48 which meshes with a worm wheel 49 on a shaft 50 coaxial with the drive shaft 37 and adapted to be coupled to the latter by an electromagnetic friction clutch 51.

With this arrangement, the motor 38, which is a reversible A.C. motor, may be activated alone to produce the initial expansion of the hone 10 by moving the expander rod 31 downwardly at a relatively rapid rate through the shank 11 to bring the stones 27 rapidly into engagement with the bore wall 14 or close to the latter thereby reducing the time consumed by this operation. The rapid expand motor then is deactivated and the feed motor 39 is activated to produce the slower expansion necessary for the stock removing portion of the honing cycle. The feed motor preferably is a variable speed DC. motor. In this instance, both motors are energized at the start of the honing cycle but the feed clutch 51 is deenergized to disengage the feed motor until rapid expansion is completed. Then the rapid expansion motor is shut off and the feed clutch is energized to couple the shafts 37 and 50 together. Accordingly, the nut 32 is turned at a relatively slow rate by the feed motor during the remainder of the honing cycle. As the cycle is terminated, the feed clutch is disengaged and the motor 38 is energized to run reversely and rapidly collapse the hone, that is, move the expander rod upwardly relative to the hone and relieve the pressure between the stones 27 and the bore wall 14.

During the rough honing operation, the progressive enlargement of the work bore 14 is sensed by a sizing device which includes means for sensing the enlargement of the bore and producing a signal indicating the attainment of the desired rough honed size. As shown in FIGS. 1 through 5, the sensing means may take the form of a sizing plug comprising a ring 52 telescoped onto and secured to the lower end of a sleeve 53 telescoped loosely over the shank 11 above the hone with a plurality of hardened segments 54 secured as by brazing to the outer periphery of the ring. These segments are externally sized to enter the work bore 14 as shown in FIG. 2 when the bore reaches the desired size. The lower end of the ring 52 is chamfered to form a beveled surface 55 which enters the bore in advance of the segments and causes the plug to center itself in the bore as permitted by the narrow radial clearance 57 between the interior of the sleeve 53 and the exterior of the shank.

To urge the plug 52 into the upper end of the work bore 14 during each down stroke of the hone 10, a coiled compression spring 58 is telescoped over the shank 11 and disposed between a collar 59 adjustably secured to the shank by a set screw 60 and a disk 61 fast on the upper end of the sleeve 53. The disk is formed with a center hole through which the shank loosely projects. As the hone moves downwardly and approaches the lower end of the bore, the spring is compressed between the collar and the ring and thus presses the plug downwardly into the upper end of the bore. If the bore is under size, the spring yields to permit the shank to continue downwardly after the plug is stopped by the workpiece. When the bore reaches the desired size, the spring presses the plug fully into the bore. An abutment 62 (FIG. 1) on the top of the hone picks up the sleeve and carries it upwardly out of the bore as the hone moves upwardly.

In this instance, the full entry of the rough sizing plug 52 into the work bore 14 is sensed and signalled by a socalled high frequency carrier-operated transducer or proximity pick-up unit 63 mounted on a bracket 64 on the frame 16 and disposed above the workpiece and alongside the shank 11. Generally stated, such units include an outer shell composed of non-conducting material enclosing a coil 65 (FIG. 8b) which is associated with a voltage source and an amplifier 65a. When a metallic mass is brought near the end of the shell, a substantially constant voltage is produced. When the exciting mass is removed, the voltage drops to zero. In the present instance, the exciting mass is a metal ring 67 secured to the disk 61 on the upper end of the sleeve 53 and normally disposed above the level of the pick-up unit. When the plug 52 moves downwardly into the work bore, however, the ring is carried downwardly to a position directly opposite the pick-up unit which thus generates a signal indicating attainment of the desired rough honed bore size.

After the rough honing operation is completed, it is customary to perform a supplemental 'or finish honing operation during the final portion of the honing cycle under reduced honing pressure obtained by terminating expansion of the hone 10 and allowing the pressure between the stones 27 and the wall 14 to play out or spark out as additional stock is removed from the bore wall. The increase in the bore size during such supplemental honing, and also the exact nature of the finish on the wall, have been largely matters of approximation and have been controlled only to the extent of holding the finishing operation to a preselected time interval or preselected number of finishing strokes in hopes that the variations in size and quality of the finish will be Within acceptable tolerances.

In accordance with the present invention, expansion of the hone 10 is continued during the final portion of the honing cycle but at a substantially reduced rate, and termination of both the rough honing operation and the finish honing operation are controlled by the sizing device which acts successively to sense and signal not only the attainment of the desired rough honed size but also the attainment of the precise finish honed size. In

this manner, reduced honing pressure is obtained for finishing the bore wall 14 without sacrificing control over the bore size or finish obtained, and approximation and guesswork as to the finished bore size and finish are eliminated.

Instead of terminating the forward operation of the feed motor 39 as in prior machines of this type, the signal produced by the proximity pick-up unit 63 upon full entry of the rough sizing plug 52 into the work bore 14 selects a slower speed for the feed motor and maintains the energization of the latter throughout the finish honing operation. The rate of hone expansion during rough honing preferably is on the order of double the rate of expansion during finish honing. For example, the rough honing expansion rate may be .024 to .030 of an inch per minute while the finishing expansion rate is .012 to .015 of an inch per minute. Thus, the finishing pressure is substantially reduced as compared to the rough honing pressure but remains substantially constant during the finishing operation to improve the bore finish while continuing the gradual enlargement of the bore as the latter is brought up to the precise finished size.

In the form shown in FIGS. 1 through 6, the means for sensing the attainment of the desired finished bore size comprises a second sizing plug in the form of a ring 68 telescoped onto the sleeve 53 above the rough sizing plug 52 and having a plurality of hardened segments 69 secured as by brazing to its outer periphery and externally sized to enter the work bore as shown in FIG. 4 when the bore reaches the desired size. The two rings are formed with interfitting axially extending jaws 70 and are telescoped onto the sleeve adjacent its lower end which is made of reduced diameter to form a downwardly facing radial shoulder 71, and are held against each other and against the shoulder by a retaining ring 72 seated in an annular groove in the sleeve immediately below the ring 52.

While the full entry of the plug 68 into the work bore 14 may be signaled in various ways, herein an apertured metal disk 73 is mounted on the frame 16 in a fixed position below the ring 67 on the sleeve 53 and is positioned to be engaged by the ring 67 as the plug 68 enters the work bore. These two elements form a switch in the control circuit for the machine as shown schematically in FIG. 812 at 74, and the closure of this switch initiates termination of the finishing operation and the honing cycle.

An alternate form for the sensing and signaling device is shown schematically in FIG. 7. In this instance, the progressive enlargement of the bore 14 during rough honing is gaged in a well known manner through the use of pressure impelled jets of fluid directed against the bore wall through nozzles 74 on the hone body 28, and means responsive to the back pressure in the nozzles is provided to signal the presence of a back pressure indicating that the bore has been enlarged to the desired size. Such a sensing device is described in detail in Patent No. 2,777,257 -to which reference is made for details of construction and operation not included herein.

In general, such devices include a source 77 of fluid under pressure which communicates through a delivery passage 78 with the nozzles 75 on the hone body and also communicates with a sump (not shown) through a second passage 79 and a restriction 80 therein. As fluid is directed through the delivery passage and the nozzles against the bore wall 14 and escapes around the hone body 28, a predetermined back pressure exists in the delivery passage. This pressure is a measure of the size of the bore and decreases as the bore size increases.

The means for signaling the desired rough honed size comprises a switch 81 operated by movement of the end wall of a bellows 82 having an interior communicating with the delivery passage 78. As the back pressure decreases, the bellows contracts and permits the switch to close to initiate the finish honing operation as soon as the bore attains the desired rough honed size. To signal the attainment of precise finished size, a second pressure operated switch 83 closes when the back pressure in the delivery passage 78 reaches a predetermined lower value corresponding to the finished size. This switch preferably is operated by the same bellows 82, which continues to contract gradually during the finish honing operation and closes the switch 83 after a preselected additional amount of bore enlargement. Closure of the switch 83 initiates the termination of the finish honing operation and the honing cycle. To eliminate the detrimental influence of changes in the supply pressure, a second bellows 85, preferably is provided for the switches 81, 83 and communicates with the passage 79 to exert a secondary control pressure on the switches in opposition to the pressure of the bellows 82 as fully explained in the aforesaid patent. Of course, there are many different types of well known sensing devices which may be used for controlling the honing operation in response to the pressure changes.

OPERATION Typical circuitry for controlling the full honing cycle is shown in FIGS. 8:: and 81). When all the control circuits are deenergized, the various relays will be deenergized and the switches thereof positions as shown. With the tool head 13 fully retracted, the hone collapsed, the spindle drive motor 17 and the pump motor 25 stopped, and a workpiece positioned for honing, the machine is started by manually closing a start switch 88 (FIG. 8a) which completes a circuit through a normally closed stop switch 89 and a relay M2 across 'two power lines L1 and L2 from a suitable A. C. power source (not shown).

The relay M2 closes its switches M22 to energize the hydraulic pump motor 25 and also closes a switch M21 through which the cycle of the machine is started upon the manual closure of a cycle switch 90 and energization of a relay CR1 whose switch CR11 closes to energize the solenoid CR5 of a by-pass valve 91. When the solenoid is energized, the valve directs the pump output to the cylinder through a control valve 92. The latter is operated by two solenoids 93 and 94 acting on the opposite ends of the valve spool to shift the same back and forth. When the down solenoid 93 is energized, pressure fluid flows through the valve to the upper end of the cylinder to lower the head 13, and when the up solenoid 94 is energized, fluid flows through the valve to the lower end of the cylinder to raise the head.

During the honing cycle, a control disk 95 is oscillated back and forth by a chain 97 connected to the head 13, turning clockwise (FIG. 8a) as the head is lowered and counterclockwise as the head is raised. At the beginning of the cycle, the disk is disposed in the position shown in FIG. 8a with a dog 98 on the disk holding a switch LS11 open. An arm 99 pivoted adjacent one of its ends to rock about the disk axis is angularly positioned as shown with a cam 100 on the arm spaced from a follower lever 101 which controls the operation of three switches LS13, LS13A and LS13B. Initially, the switch LS13A is closed in the circuit of the down solenoid 93 and the switch LS13 is held open in the circuit of the up solenoid 94.

Thus, when the pump motor is started and the solenoid CR5 is energized, pressure fluid is directed by the control valve 92 to the upper end of the cylinder 20 to start the head 13 down to carry the collapsed hone 10 toward and into the work bore 14. During the initial part of this movement, the dog 98 passes the actuator for the switch LS11 and allows the latter to close thereby completing holding circuits for the relays CR1 and CR5 through the then closed switches CR11 and CR12. As the hone approaches the lower end of the work bore, a lug 102 on the disk engages the arm 99 and shifts the latter clockwise far enough to bring the free end of the arm into engagement with the operator 103 of a switch LS12 and close the latter in the circuits of a hone expansion relay CR7 and a spindle rotation relay CR8. When energized, the latter starts the spindle motor 17 and the relay CR7 closes its switch CR71 (FIG. 8b) to complete a circuit to a relay MP3 which starts the rapid expansion motor 38 in expanding direction by closing its switches M1 31. At the same time, closure of switch CR73 energizes a relay M6 through normaly closed switch CR101 and this relay closes its switch M61 to start the feed motor 39. Switch MF32 opens in the circuit of the clutch 51 and thereby disengages the feed motor. Thus, the motor 38 expands the hone rapidly within the work bore 14 while the feed motor idles.

Rapid expansion may be terminated in various ways as by a device for sensing full engagement of the stones 27 with the bore wall 14. To simplify this disclosure, however, let it be assumed that expansion is terminated in response to opening of a switch LS18 (FIGS. 6 and 8b) by a cam 194 on a stubshaft 105 journaled in the housing 33 and rotated through a rack and pinion connection 107 with the expander rod 31. Thus, as the rod moves downwardly and expands the hone 10, the cam 104 turns with the stubshaft and engages the switch actuator after a preselected amount of rapid hone expansion. When the switch LS18 is opened, relay MP3 is deenergized and opens switches MF31 to stop the rapid expansion motor. At the same time, switch MF32 is closed to energize the feed clutch 51 and start the gradual rough honing expansion of the hone by the feed motor 39.

As the gradual expansion of the hone 10 continues, the hone is reciprocatecl back and forth through the work bore 14 in the following manner. As the hone approaches the lower end of the work bore, the lug 102 on the disk 95 shifts the arm 99 clockwise far enough to cause the cam to move the follower lever 101 outwardly about its fulcrum and close the switch L813 to energize the up solenoid 94 while opening the comp-anion switch LS13A in the circuit of the down solenoid 93. Accordingly, the spool of the control valve 92 is shifted to its alternate position and directs fluid to the lower end of the cylinder 20 to start upward movement of the head and counterclockwise rotation of the control disk. As the hone approaches the upper end of the bore 14, a second lug 108 on the disk swings the lever 99 counterclockwise until the cam 100 reverses the switches LS13 and .LS13A and initiates the next down stroke, this being accomplished before the hone has been withdrawn from the bore. The amount of shifting of the arm during the honing operation is not sufficient to carry the end of the arm off the switch L812 which thus remains closed during successive honing strokes of the tool. Accordingly, reciprocation of the hone in the bore and the rough honing continue under the control of the oscillating disk 95.

Near the lower end of each down stroke of the hone 10 through the work bore 14, the beveled end 55 of the rough sizing plug 52 is pressed into the work bore. During each stroke before the bore attains the desired rough honed size, however, the bevel abuts against the workpiece 15 and stops the plug with the ring 67 above the proximity pick-up unit 63 as shown in FIG. 1, and the shank 11 continues downwardly through the sleeve 53 as permitted by the yielding of the spring 58. When the bore finally attains the desired size, the plug is pressed fully into the upper end of the bore and the exciting ring moves downwardly to the position shown in FIG. 2 alongside the pick-up unit. The signal generated by the latter in response to the proximity of the ring energizes the coil 1419 of a sensitive relay SCR2 which closes its switch SCR21 to seal itself and also closes a switch SCRZS while opening a normally closed switch SCRZZ. As will be seen in FIG. 8b, the switches SCRZZ and SCR23 are in parallel lines L3 and L4 connected to the input terminal of a full wave bridge rectifier 110 in the DC. circuit of the feed motor 39. The line L4 is connected to the wiper 111 of a potentiometer 112 in line L3 and the latter extends between a power line L7 and the wiper 113 of a second potentiometer 114. The potentiometer 114 is in a line L8 connected across the power lines L7 and L9 in parallel with lines L19 and L11 conmeeting the power lines to the input terminals of a rectifier 1% in the circuit of the feed clutch 51.

With this arrangement, the current flow through the DC. motor and the speed thereof during rough honing, that is, when the switch SCRZZ is closed and the switch SCR23 is open, is determined by the potentiometer 114 and the voltage drops across the wiper 113 and line L7, while the motor speed when the switch SCR23 is closed depends upon the selected settings of both potentiometers and is substantially reduced, as compared to the rough honing speed, by the reduction in the voltage drop across the input terminals of the rectifier 110. Accordingly, energization of the relay SCRZ when the bore attains the desired rough honed size immediately reduces the motor speed and the rate of hone expansion to initiate the finish honing operation without interrupting the honing cycle. While the elements 112 and 114 are shown schematically and described herein as potentiometers in the interest of simplicity, it will be evident to those skilled in the art that similarly disposed variable transformers may be used to advantage in place of the potentiometers.

During the subsequent down strokes of the hone, the rough sizing plug 52 enters the upper end of the bore 14 and the segments 69 on the finish sizing plug 68 abut against the workpiece 15, stopping the sleeve 53 before the contact ring 67 engages the contact disk 73. Because closure of the switch SCRZI completed a holding circuit for the relay SCRZ, the rough sizing means are, in effect, disabled to maintain the slower rate of expansion throughout the finish honing operation. With the feed motor 39 running at a selected slow speed, the hone 10 is expanded slowly but at a constant rate to finish the bore wall 14 while bringing the latter up to size. When the finish sizing plug enters the bore, the ring 67 engages the disk 73 and closes the switch 74 to initiate termination of the honing cycle. In this instance, this is accomplished by completing a circuit to a sensitive relay SCRl which opens its switch SCR11 to break the circuit to the relay M6 to deenergize the latter and thereby open the switch M61 to stop the feed motor 39. At the same time closure of a switch SCR12 activates a timer TDS which may be of any well known construction. When the timer times out, after a suitably short interval such as two or three seconds, it closes its switch TD51 to initiate withdrawal of the home 10 from the work bore 14. The very short interval of additional honing after the finish sizing plug enters the bore is desirable primarily for its effect in truing the bore to geometrical uniformity along its full length. It should be understood, however, that the interval is very short as compared to the intervals required for the supplemental honing operations of prior machines, and results in the removal of very little stock from the bore wall. Accordingly, the effect of the additional honing on the finished bore size is negligible.

Herein, the switch TD51 completes a circuit to a relay CR6 through the switch LS13B, which is closed only during up strokes of the hone, and the relay CR6 closes its switch CR62 to override the normal reciprocation control and hold the energization of the up solenoid 94- when the switch L813 is opened by the cam 100 at the upper end of the normal working stroke of the hone. At the same time, relay CR6 opens its switch CR64 to deenergize the relay CR7 which closes its switch CR72 to energize a relay MR3 thereby closing switches MR31 and starting the motor 38 in reverse to collapse the hone. The opening of a switch MR32 deenergizes the feed clutch 51 and :disengages the feed motor 39 before the shaft 37 starts to turn reversely.

Thus, the hone is collapsed as it is withdrawn from the finished work bore. A second cam 104A (FIG. 6) turning with the shaft 1% opens a switch L815 (FIGS. 6 and 8b) to deenergize the relay MR3 and stop the motor 38 when the hone is fully collapsed. As the hone 11 continues upwardly out of the bore, the lug 1G8 swings the arm 99 past the switch LSlZ and permits the latter to open. When the lug 98 on the control disk engages the operator of the switch L811 and opens the latter, the solenoid CR5 is deenergized and the spool of the by-pass valve 91 is returned to its original position to stop the flow of pressure fluid through the control valve 92 to the cylinder 20. Accordingly, the head comes to rest with only the pump motor 25 running and with the hone 10 fully retracted from the work bore 14 in position for en try into the next bore to be honed. After a new workpiece has been positioned for honing, another honing cycle may be initiated by again closing the manually operable cycle switch 91).

The manner of modifying the control circuit to incorporate the pressure operated switches 81 and 83 of FIG. 7 will be readily apparent to one skilled in the art. Instead of using the proximity pick-up unit 63 to energize the relay SCRZ in response to attainment of the rough honed bore size, closure of the switch 81 completes an energizing circuit for the relay. Similarly, the second pressure switch 83 is substituted for the switch 74 formed by the contact members 67 and 73. In all other important respects, the control circuits may be the same. The sensitive relays SCR1 and SCRZ may be of any well known construction such as those manufactured and sold by Cutler Hammer, Milwaukee, Wisconsin, as Model No. 13535ED5, and the proximity pick-up unit may be that sold by Electro Products, Chicago, Illinois, as Model No. 4910AN.

Using the improved mechanism described above, it is possible to rough and finish hone work bores in a substantially continuous operation while maintaing precise control of the finish and the bore size obtained. The successively acting sizing device senses and signals the attainment of both the rough honed bore size and the fiinish honed size whereby the finishing operation may be terminated immediately upon attainment of the desired size or so closely thereafter that the bore size is held within very close tolerances. In this manner, guesswork as to the final bore size and variations in the quality of the fiinish are eliminated.

I claim as my invention:

1. In a machine for rough and finish honing the wall of a bore in a workpiece in a substantially continuous honing cycle, the combination of, an expansible honing tool, mechanism for rotating said tool and reciprocating the same back and forth through said bore, feed mechanism for expanding said tool first at a relatively fast rough honing rate and then at a slower finish honing rate, a rough sizing plug axially alined with said tool and supported adjacent one end of said bore for back and forth movement toward and away from the latter, said rough sizing plug being sized to be stopped at the end of said bore wall when the bore is under a predetermined rough size but to enter the bore when the latter attains such rough size, a finish sizing .plug axially alined with said tool and supported adjacent one end of said bore for back and forth movement toward and away from the latter, said finish sizing plug being sized to be stopped by the end of said bore wall when said bore is under a predetermined finished size larger than said rough size but to enter the bore when the latter attains said finished size, a device for sensing the entry of said rough sizing plug into said bore during rough honing thereof and contnolling said feed mechanism to reduce the rate of expansion of said tool to said finish honing rate, and a second device i or sensing the entry of said finish sizing plug into said bore and controlling said mechanism to initiate termination of the honing action in response to such entry.

2. In a machine for rough and finish honing the Wall of a bore in a workpiece in a substantially continuous honing cycle, the combination of, an expansible honing tool, drive mechanism for rotating said tool and simultaneously reciprocating the same b ack and forth through said bore, feed mechanism .for expanding said tool at a first rate sufficient to maintain rough honing pressure on said bore wail and then at .a second slower rate to finish home said wall, and a successively acting sizing device including first means 'for sensing the attainment of a first predetermined bore size and cont-rolling said feed mechanism to terminate the rough honing action and initiate the finish honing, and second means for sensing the subsequent attainment of a second predetermined bore size lamger than said first size and controlling said mechanism to initiate termination of said finish honing action and the honing cycle.

3. The combination defined in claim 2 in which said sizing device includes first and second coaxial sizing plugs 10 axially alined with said tool and supported in axially spaced relation on said machine for back and forth movement toward and away from one end of said bore, said first plug having an outside diameter equal to said first bore size and said second plug having an otuside diameter equal to said second bore size.

4. The combination defined in claim 2 in which said sizing device includes at least one nozzle on said honing tool for projecting a jet of fiuid under pressure against said bore wall, and said first and second sensing means are responsive to decreases in the back pressure in said nozzle and open-able to signal the presence of back pressures indicating the attainment of the respective bo-re sizes.

5. The combination defined in claim 2 further including means for activating said second sensing means and disabling said first sensing means after the latter indicates attainment of said first bore size.

References Cited by the Examiner UNITED STATES PATENTS 1,751,204 3/1930 Kempton et al. 51-165 2,819,566 1/1958 Johnson 51165 X 2,820,328 1/ 1958 Calvert 51--165 X 2,821,049 1/1958 Harris 5l-165 X LESTER M. SWINGLE, Primary Examiner. 

2. IN A MACHINE FOR ROUGH AND FINISH HONING THE WALL OF A BORE IN A WORKPIECE IN A SUBSTANTIALLY CONTINUOUS HONING CYCLE, THE COMBINATION OF, AN EXPANSIBLE HONING TOOL, DRIVE MECHANISM FOR ROTATING SAID TOOL AND SIMULTANEOUSLY RECIPROCATING THE SAME BACK AND FORTH THROUGH SAID BORE, FEED MECHANISM FOR EXPANDING SAID TOOL AT A FIRST RATE SUFFICIENT TO MAINTAIN ROUGH HONING PRESSURE ON SAID BORE WALL AND THEN AT A SECOND SLOWER RATE TO FINISH HONE SAID WALL, AND A SUCCESSIVELY ACTING SIZING DEVICE INCLUDING FIRST MEANS FOR SENSING THE ATTAINMENT OF A FIRST PREDETERMINED BORE SIZE AND CONTROLLING SAID FEED MECHANISM TO TERMINATE THE ROUGH HONING ACTION AND INITIATE THE FINISH HONING, AND SECOND MEANS FOR SENSING THE SUBSEQUENT ATTAINMENT OF A SECOND PREDETERMINED BORE SIZE LARGER THAN SAID FIRST SIZE AND CONTROLLING SAID MECHANISM TO INITIATE TERMINATION OF SAID FINISH HONING ACTION AND THE HONING CYCLE. 